3. Infection

Question 1

With regard to osteomyelitis, radiographs will be normal for

Answer 1

7-10 days

Question 2

Osteomyelitis spread in children and adults

Answer 2

Children have hematogenous spread usually hitting the long bones (metaphysis). Adults are more likely to have direct spread (in diabetic).

Question 3

General rule in osteomyelitis

Answer 3

Septic joints more common in adults.

Osteomyelitis more common in kids.

Question 4

Classic look of osteomyelitis

Answer 4

Hallmarks are destruction of bone and periosteal new bone formation.

Question 5

Osteomyelitis in Spine =

Answer 5

IV drug user

Question 6

Psoas Muscle Abscess =

Answer 6

TB

Question 7

Unilateral SI joint =

Answer 7

IV drug user

Question 8

Osteomyelitis in Spine with Kyphosis (Gibbus Deformity) =

Answer 8

TB

Question 9

Sequestrum

Answer 9

Piece of necrotic bone surround by granulation tissue

Question 10

Involucrum =

Answer 10

Thick sheath of periosteal bone around sequestrum

Question 11

Cloaca =

Answer 11

Defect in the periosteum (bone skin) caused by infection

Question 12

Sinus Tract

Answer 12

A channel from the bone to the skin (lined with granulation tissue).

Question 13

Chronic Osteomyelitis:

Answer 13

This is defined as osteomyelitis lasting longer than 6 weeks.

Question 14

Draining sinus tracts are a risk factor for

Answer 14

squamous cell CA

Question 15

Most specific sign of active chronic osteomyelitis

Answer 15

presence of a sequestrum (best shown with computed tomography)

Question 16

MRl diagnosis of healed osteomyelitis is based on =

Answer 16

Return of normal fatty marrow

Question 17

Acute Bacterial Osteomyelitis

Answer 17

3 categories

1) hematogenous seeding {most common in child)

2) contiguous spread

3) direct inoculation of the bone either from surgery or trauma.

Question 18

Acute hematogenous osteomyelitis has a predilection for the long bones of the body, specifically the

Answer 18

MEtaphysis

which has the best blood flow and allows for spreading of the infection via small channels in the bone that lead to the subperiosteal space

In the slightly older baby (<18 months) these vessels from the metaphysis to the epiphysis atrophy and the growth plate stops the spread (although spread can still occur). This creates a “septic tank” effect. This same thing happens with certain cancers (leukemia); the garbage gets stuck in the septic tank (metaphysis). Once the growth plates fuse, this obstruction is no longer present.

Question 19

Answer 19

Osteomyelitis

Low signal in the bone marrow on T1 imaging adjacent to an ulcer or cellulitis is diagnostic.

Question 20

The Ghost Sign: Neuropathic Bone vs
Osteomyelitis in a Neuropathic Bone

Answer 20

A bone that becomes a ghost (poor definition of margins) on T1 imaging, but then re-appears (more morphologically distinct) on T2, or after giving IV contrast, is more likely to have osteomyelitis.

Question 21

Discitis / Osteomyelitis mechanism

Answer 21

Infection of the disc and infection of the vertebral body nearly always go together.

The reason has to do with the route of seeding;

Question 22

Answer 22

Typical Look of Discitis / Osteomyelitis

Question 23

Answer 23

Epidural Abscess

This is an infected collection between the dura and periosteum.

Question 24

Discitis / Osteomyelitis Trivia

Answer 24

Adults: Surger, procedue, systemic infection
Children: <5 = hematogeneous spread
Most common bug: Staph A - IV drug
Almost always ESR and CRP are elevated

Question 25

Pediatric Discitis I Osteomyelitis

Answer 25

Children have direct blood supply to the intervertebral disc, so they can get isolated discitis.

Isolated Discitis is basically never seen in adults

Question 26

Kid (< 4y.o.) + URTI + back pain =

Answer 26

Think of Pediatric discitis

Question 27

Pott Disease

Answer 27

“spare the disc space”
have multi-level thoracic “skip ’ involvement

Buzzwords:
“Large paraspinal abscess”
“Calcified Psoas Abscess ”
“Gibbus Deformity ”

Question 28

‘‘Gibbus Deformity”

Answer 28

Question 29

Answer 29

TB spondylodiscitis

Question 30

DDxfor Pott’s Disease

Answer 30

Question 31

What can also have disc space preservation?

Answer 31

Brucellosis

Question 32

Answer 32

“‘Tuberculosis Dactylitis” (Spina Ventosa)

Kids + Short tubular bones of the hands and fit

diaphyseal expansile lesion with soft tissue swelling.

Question 33

Answer 33

‘‘Rice Bodies”

These are sloughed, infarcted synovium seen with end stage RA, and TB infection ofjoints

Question 34

Septic Arthritis

Answer 34

You see this the most in large joints which have an abundant blood supply to the metaphysis (shoulder, hip, knee).

IV drug users will get it in the SIjoint, and sternoclavicularjoint.

Question 35

Answer 35

Septic Arthritis

Loss of joint space + Destriction + osteopenia

Question 36

Pneumoarthrogram Sign

Answer 36

If you can demonstrate air within a joint you can exclude a joint effusion.

No joint effusion = No septic joint

Question 37

Necrotizing Fasciitis

Answer 37

Very bad = kills very quickly = rare

Hx = HIV, Transplan, DM, alcoholics

From Group A strep

GAS in soft tissues

Question 38

Necrotizing Fasciitis in Scrotum =

Answer 38

Fournier Gangrene